The objective of the proposed work is to investigate the role of environmental chemicals as co-toxicants. This approach is based on the knowledge that many chemicals are present together in the ecosystem and, therefore, may act to potentiate the effects of other chemicals. Specific experiments will investigate the effect of environmental chemicals (insecticides, herbicides, etc.) on the effects of known toxicants. The models proposed included interactions in drug metabolism, blood dyscrasias, hepatotoxicity and destruction of cytochrome P-450. The approach outlined above should aid in evaluating the possible harmful effects of environmental chemicals acting in concert.